Emotions after victory or defeat assessed through qualitative behavioural assessment, skin lesions and blood parameters in pigs

• Aggression is a pig welfare issue but pigs’ emotional experience of it is unknown.
• Emotions of pigs which had just won or lost a fight were assessed through QBA.
• The main dimensions were ‘relaxed/tense’ (valence) and ‘active/listless’ (arousal).
• Positive valence related to low arousal in winners but to high arousal in losers.
• Physical injury and effort correlated with terms indicating emotional distress.

Aggression between pigs causes injuries and production losses and is a long standing animal welfare issue. Although the physiological impact of aggression has been well described, little is known about the emotional experience of aggressive interactions. Our aim was to investigate the emotional expression of winners and losers after a fight and how this relates to costs of fighting. Emotions were studied through use of Qualitative Behavioural Assessment (QBA), a method where participants qualitatively assess the emotional expression of animals seen live or on video. Eighteen pig farmers watched 28 short video clips of pigs which had just won (n = 14) or lost (n = 14) a fight. Farmers rated the pigs’ emotions based on a pre-existing list with 21 descriptors of emotions, while being unaware of the contest outcome (winner/loser). Scores were analysed by a Principal Component Analysis (PCA), which resulted in two factors combining the 21 descriptors into four expressive quadrants. Factor 1 ranged from relaxed/content to tense/frustrated, thereby describing valence (explaining 43% of total variance), and factor 2 ranged from active/lively to listless/indifferent, describing arousal (explaining 16%). Winners (W) and losers (L) did not significantly differ in their expression of valence (W −0.19 ± −0.20;  L 0.16 ± 0.17; P = 0.16) or arousal separately (W −0.07 ± 0.22; L 0.06 ± 0.18; P = 0.51), but did in the valence-arousal interaction (P = 0.02). In winners a high valence related to low arousal whereas in losers high valence related to high arousal. In addition, winners were observed as more negatively affected than losers by a high number of skin lesions (P < 0.01). QBA scores significantly correlated with skin lesions (skin lesions positively correlated with 12 descriptive QBA terms reflecting impaired welfare), blood lactate (curious r = −0.41; lively r = −0.44; playful r = −0.40; positively occupied r = −0.39), blood glucose (distressed r = 0.40; fearful r = 0.39; playful r = −0.38) and the contest duration (sociable r = −0.39) (all P < 0.05). This shows that skin lesions not only reflect physical injury but can also be associated with a negative emotional state, which adds value to their use as a welfare assessment tool. The use of QBA in this study sheds light on the complex ways in which animals emotionally perceive aggression and physical injury. Further studies of this kind will enable better understanding of the true welfare impact of aggressive interactions.